Producing lubricating oils by irradiation



, States No Drawing. Filed Dec. 14, 1956, Ser. No. 628,214 8 Claims. (Cl. 204-154) The present invention proposes a process for producing lubricating oils from select hydrocarbon mixtures by irradiation.

In brief compass, this invention proposes a process which comprises exposing a distillate hydrocarbon mixture, comprising predominantly parafiinic hydrocarbons and a minor amount of unsaturated straight chain hydrocarbons, to irradiations. The radiation comprises neutrons and gamma rays obtained from a nuclear reactor. The irradiation is carried out at a temperature below 600 F. until more than about 100 equivalent meg'aroentgens of irradiation have been absorbed. In this manner, a high quality lubricating oil amounting to about 50 to 90 weight percent on feed is obtained. This oil has a viscosity index above 125.

It has previously been known to convert cetane (n hexadecane) to lubricating grade oils through the use of radiation obtained from an atomic pile. Lubes boiling in' the range of 700-900" F. obtained in this manner have a viscosity of about 38 SSU at 210 F. and a V1. of about 150. The yields are, however, relatively lowabout 10-15 weight percent on feed, and the feed is, of course, expensive. Cetane also has the undesirable tendency to pass rather quickly through the satisfactorily lubricating viscosity range during irradiation, and to be easily-converted to a rubbery solid.

Further experimentation with apparently similar feed stocks has shown that the production of high quality lubricating oils by irradiation is dependent to an unpredictable extent on the characteristicsof the feed material. It has now surprisingly been found that catalytically cracked materials that have been treated to remove aromatics and naphthenes, surprisingly produce a high quality lubricating oil when irradiated using radiation obtained from a nuclear reactor, i.e., radiation comprising neutrons. Such catalytically cracked and treated hydroca'rbon' mixtures predominate in saturates or paraflins, and contain a minor but appreciable amount of olefins produced by the cracking.

Because olefins polymerize easier than paraflins, it is unexpected that the olefin-containing mixture does not go to a solid as does cetane under the same degree of radiation. Further, theolefin containing mixture gives a surprisingly high yield, as compared to cetane, of liquid materialf'The yield is above 50 weight percent. and usually is over 75 weight percent, based on feed to the radiation zone. i

Thus an important feature of the presentinvention is the discovery of an inexpensive feed stock that can satisfactorily be converted in good yields to high quality lubricating oils, using radiation comprising neutrons.

The hydrocarbon mixture or petroleum fraction used as a feed stock in the present invention boils in the range of300 to 700 F. It contains 70 to 95 Weight percent voi essentially saturated hydrocarbons, 5 to 40 weight percent unsaturated or olefinic' straight chain hydrocarbons,

less than 2 weight percent of aromatics and less than 25 weight percent "of 'cyclo parafiins or naphthenes. By aromatics 'are'meant hydrocarbons consisting of one or more aromatic ringssu'ch as benzene, and anthracene. By naphthenes is meant cyclic compounds that are fully saturated. It is essential that the olefin content be within the range above indicated. It has been found that at atent ranges higher than this, the yield and quahty of the lubricating oil falls off, although the reason for this is. not clearly understood at this time. With smaller amounts of olefins than specified, the surprising results of this invention are lost and the process approaches that of irradiating cetane, wherein the tendency to be overconverted is present, and the yield greatly falls ofi.

While the select hydrocarbon mixture used in the present invention can be obtained from many sources, a particularly preferred source is to start with a catalytically cracked distillate. Such processes, well known in the art, as fluid catalytic cracking, fixed bed cracking, or suspensoid cracking using catalysts such as silica'alumina, natural clays, boria-alumina, and silica-magnesia can be used. Generally the feed stocks to such catalytic cracking processes boil in the range of 430 to l000- F. The

processes are operated at a temperature in the range of 850 to 1050 F. and feed rates in the range of 1 to 2 w./hr./w. (pounds of feed per hour per pound of catalyst). This catalytic cracking step serves to dehydrogenate the naphthenes in the feed stock and to produce some olefins. V

Such a catalytically cracked mixture in the preferred embodiment of this invention is separated as by distillation and then is treated to remove aromatics. This is preferably done by a conventional extraction process using a liquid solvent, such as sulfur dioxide, fur fural, nitrobenzene, 2,2f dichlor-ethyl-ether, phenol, etc. The yields are in the range of 20 to 90 weight percent, on the cracked feed stock, depending on the aromatic content.

In a much preferred embodiment of the invention, the material so extracted is then further cleaned up using a solid absorbent, such as silica gel, clays, molecular sieves, etc. These treating steps usually result in a yield of over 40 weight percent, based upon the theoretical yield of raflinate of material having the above-described characteristics.

Other types of cracking processes can be used, such as fluid coking, delayed coking, thermal cracking, and steam cracking. Generally these processes convert distillates and/or'residua at temperatures above about 900 F. up to about 1400 F., and serve to introduce some olefins into the feed stock and to condense the naphthene structures. In the case, however, where the feed precursor is not a catalytically cracked material, it is preferred .to use a molecular sieve to extract the straight chain paraflins and olefins from the cracked mixture.

These molecular sieves are becoming known in the art,

and are composed of select inorganic materials such as oxides of aluminum and silicon containing exchanged cations such as sodium or calcium, having regulated pore desired feed mixture composed of saturates and olefins is obtained.

Other sources of feed can be used. For example, a

predominantly parafiinic feed stock can be adjusted to have the proper proportion of ingredients by the addition of olefins. For example, a paraflin wax can be modified to obtain the feed stock of the present invention by the addition of olefins having from 12 to 24 carbon atoms, to arrive at the above specified mixture. Feed stocks that contain an excess of olefins can be adjusted in olefin content by suitable treatment, such as with sulfuric acid or hydrogenation. These methods of olefin addition or extraction can, of course, be used to adjust the olefin content of the above described feed stocks made through thermal or catalytic cracking.

At present it is beheved that it is essential that. the radiation be obtained from a nuclear reactor, such as an atomic pile, so that it contains neutrons among othertypes of radiation.

Generally the effective radiation obtained from a nuclear reactor comprises neutrons and gamma rays, while there may be present other types of radiation, such as alpha and beta. It is further believed that to obtain the best results according to this invention, the gamma rays must have an energy predominantly above 1 mev. There are several types of nuclear reactors known in the art, such as the earlier graphite moderated atomic piles and the later developed water-moderated reactors. The form of the nuclear reactor is not important to the present invention.

The material to be irradiated can be exposed either batchwise or continuously, so long as the dosages and dose rates described below are obtained, and the radiation comprises neutrons. It is sufiicient to expose the material to the radiation by placing it in suitable containers or conduits contiguous to or in the radiation source. In some cases the hydrocarbon material can serve as a moderator in the nuclear reactor.

The dose rate should be at least 1 equivalent megaroentgens per hour (1.06 kwh./lb. of product). A dose rate of 10 or more equivalent megaroentgens per hour (l.06 10- kwh./lb.) can be used. The total dosage received should be at least 100 equivalent megaroentgens (0.106 kwh./lb.). In general over-radiation is to be avoided, under 1400 equivalent megaroentgens (1.48 kwh./lb.) usually being sufficient. Of the energy received, it is preferred that at least 30 percent be obtained through neutrons while the rest may come from the associated gamma rays. To obtain best results, the temperature should be below 600 F. to avoid any predominance of cracking reactions and, therefore, yield loss. Generally, the temperature can be as low as 100 F. while still obtaining suitable results. The pressure is not critical and can be substantially atmospheric or less. If desired, condensed phase conditions can be maintained by maintaining a pressure up to 500 psi. or more.

The irradiation should be carried out in the absence of a hydrocarbon conversion catalyst. What might be termed radiochemical catalysts, however, can be used, i.e., isotopes that give rise to secondary radiation upon capture of neutrons. For example, boron 10 and lithium 6 give ofi highly ionizing alpha particles and cadmium 113 gives rise to highly energetic gamma rays. Such isotopes can be used in the amount of 0.001 to 1 weight percent based on feed. They can be used as solutes; as discrete solids carried in the irradiated mixture; or can be present on the container walls.

After irradiation, the hydrocarbon mixture is separated as desired. It is preferred to separate a mixture boiling in the range of 700 to 1000 F, having a viscosity in the range of 35 to 70 SSU at 210 F. or higher, and a V1. of at least 125. The lighter material remaining can be recycled for further conversion.

The 700 to 1000 F. boiling range fraction, or any portion thereof, can be further treated as desired. It has been found that this fraction can be further improved in viscosity index by subjecting it separately to radiation in the absence of contaminating lower and higher boiling materials.

The lubricating oil so obtained can, of course, be further treated by conventional means such as extraction, dewaxing, blending with other additives such as extreme pressure agents, etc.

While the whole recovered fraction can be used as a lubricating oil with minor modification, it has been found that portions of this separated fraction, particularly the portion boiling in the range above 800 to 900 F. serve as excellent additives to other conventional lubricants to lower the pour point, increase the viscosity, and/or increase the viscosity index. Generally the higher boiling portion, boiling in the range of 800 to 1000 F., appreciably influences the characteristics of a conventional lubrieating oil when added in amounts in the range of 1 to 15 weight percent based on final composition. Excellent motor oils having viscosities in the range of 40 to 60 SSU at 210 F. and viscosity indices above can be obtained in this manner.

It has also been found that the portion of irradiated material having a viscosity in the range of 1,000 to 10,000 SSU at 210 F. when added to other lubricating oils in an amount in the range of l to 10 weight percent lowers the pour point by at least 10 F. besides serving to improve the viscosity index.

The lubricating oils obtained through irradiation according to this invention serve as excellent grease-making materials.

Example The source of the hydrocarbon material used in the present invention was a 600 to 1100 F. boiling range distillate obtained from a mixture of Venezuelan, South Louisiana and West Texas crudes. This was converted in a fluid catalytic cracking unit using a temperature of 915 F., with a silica-alumina type catalyst. A fraction boiling in the range of 350 to 500 F. and amounting to 9.4 percent on total cracked products was segregated from the catalytically cracked material. This fraction was then treated with volume percent sulfur dioxide at a temperature of -35 F. to remove aromatics. The feed contained 60 volume per cent aromatics and the raffinate from this extraction contained about 7 volume percent aromatics. The sulfur dioxide treated material was then further contacted with weight percent of silica gel.

The extracted raflinate, amounting to about 30 weight" percent on the cracked fraction, contained 87 weight percent saturates and 13.2 weight percent olefins as determined by chromatographic analysis. It had a naphthene content of 19.4 weight percent and a paraffin content of 67.4 weight percent.

600 cc. of this material were then exposed to irradiation in a vented aluminum container in the Brookhaven National Laboratories graphite-moderated atomic pile. The pressure during irradiation was substantially atmospheric. The temperature was about 300 F. The flux of thermal neutrons (having less than 0.6 mev.) was 2.5 1O n/cm. /sec. in the reaction zone. The flux of fast (above 0.6 mev.) neutrons was 1.2X10 n/cn1. /sec. The gamma ray flux was 1.6 10 roentgens per hour. The total dose rate was about 6 X10 equivalent roentgens per hour. The irradiation was continued for 10 days until about 1400 equivalent megaroentgens had been absorbed.

About 95 weight percent of the material originally introduced into the container was recovered, the rest having distilled off during irradiation. The irradiated product had the following distillation:

Weight percent based on feed 0-500 F. 14.8 SOD-700 F. 10 700-780 F. 7 780 F.+ 70 As noted before, because olefins polymerize easier than Viscosity at 210 F., SSU 53.9 Viscosity at 100 F., SSU 237.2 Viscosity index 136 For comparison, a 700900 F. boiling range lubricant made from pure cetane under substantially the same conditions at a yield of only 110-15 weight percent after 15 days of irradiation, had the following characteristics:

Viscosity at 210 F., SSU 38.4 Viscosity at 100 F., SSU 78.3 Viscosity index 150-156 Thus it can be seen that from the catalytically cracked and extracted material, a high yield of a high viscosity material is obtained.

The 780 F.+ product from the irradiation was blended in 3 percent concentration in a lubricant base stock having the characteristics listed and with the following results:

Base Stock Base Stock 3 Percent Additive Viscosity. SSU at 210 F 47. 9 51. 5 Pour Point, F +15 +5 Viscosity Index- 113 120 Ten weight percent of the 780 F.+ fraction having an approximate viscosity of 6,000 SSU at 210 F., was mixed with a base stock. The base stock consisted of 95 weight percent of a neutral, 5 weight percent of a bright stock,

and a small amount of a pour point depressant. The following results were obtained:

Base Stock Base Stock Weight Percent of Additive Viscosity, ssU at 210 F 4s. 6 5a. 4 Viscosity, SSU at 110 F 171.8 267. 2 Viscosity Index V 114 120 I polymer. It gives a higher viscosity level with less radiation, even though it is of lower viscosity than, for example, the cetane known to the prior art.

Having described this invention, what is sought to be protected by Letters Patent is succinctly set forth in the following claims.

What is claimed is:

1. A process which comprises exposing a hydrocarbon mixture boiling in the range of 300 to 700 F. and consisting essentially of 60 to 95 weight percent of saturated hydrocanbons, 5 to 40 weight percent of unsaturated hydrocarbons, less than 2 weight percent of aromatics, and less than 25 weight percent of naphthenes, to radiation comprising neutrons and gamma rays having an energy above 1 mev. obtained from a nuclear reactor, at a temperature in the range of 100 to 600 F., a dose rate above 1 equivalent megaroentgens 'per hour, until 100 to 1400 equivalent megaroentgens have been absorbed, and recovering from the irradiated mixture a high quality lubricating fraction boiling above 700 F., having a viscosity above 35 SSU at 210 F. and a viscosity index above 125 and amounting to at least 50 weight percent of said hydrocarbon mixture.

6 2. The process of claim 1 wherein said hydrocarbon mixture is obtained from a distillate boiling in the range of 430 to 1000 F. and catalytically cracked at a temperature in the range of 850 to 1050- F. to dehydrogenate naphthenes, followed by an extraction treatment using a liquid solvent to reduce the condensed ring aromatic content of the cracked material, the yield of said hydrocarbon mixture on said cracked mixture being in the range of 20 to weight percent, depending on the aromatic content.

3. The process of claim 2 wherein the extracted material is further cleaned up by treatment with a solid absorbent.

4. The process of claim 1 wherein said hydrocarbon mixture is obtained from an oil thermally cracked at a temperature in the range of 800 to 1400 F followed by treatment of the cracked oil with a molecular sieve to recover said hydrocarbon mixture.

5. The process of claim 1, wherein said hydrocarbon mixture is obtained from hydrocarbon mixtures containing an excess of olefins by treatment with sulfuric acid.

6. The process of claim 1, wherein said hydrocarbon mixture is obtained from predominantly paraflinic hydrocarbon mixtures by the addition of olefins having from 12 to 24 carbon atoms.

7. A lubricating composition having a viscosity in the range of 40 to 60 SSU at 210 F., a viscosity index above 115, and comprising a major proportion of a mineral lubricating oil and a minor proportion in the range of 1 to 15 weight percent of a material obtained by exposing a normally liquid petroleum fraction boiling in the range of 300 to 700 F. and consisting essentially of 60 to weight percent of saturated hydrocarbons, 5 to 40 weight percent of unsaturated hydrocarbons, less than 2 weight percent of aromatics, and less than 25 weight percent of naphthenes to radiation comprising neutrons and gamma rays, having an energy above one mev. and obtained from a nuclear reactor, the irradiation being carried out at a temperature in the range of to 600 F., a dose rate above one equivalent megaroentgen per hour until 100 to 1400 equivalent megaroentgens have been absorbed by said petroleum fraction, and then separating the irradiated .petroleum fraction to obtain a fraction boiling above 700 F., having a viscosity above 35 SSU at 210 F. and a viscosity index above 125, and amounting to at least 50 weight percent of said petroleum fraction, which is then blended with said mineral lubricating oil.

8. The lubricating composition of claim 7 wherein the irradiated material blended with said lubricating oil has a viscosity in the range of 1,000 to 10,000 SSU at 210 F.

References Cited in the file of this patent UNITED STATES PATENTS 2,161,987 Tilton et a1 June 13, 1939 2,197,768 Pier et al Apr. 23, 1940 2,281,979 Kimberlin May 5, 1942 2,350,330 Remy June 6, 1944 2,376,807 Pier et al May 22, 1945 2,743,223 McOlinton et a1 Apr. 24, 1956 2,744,872 Nelson May 8, 1956 2,845,388 Black et a1 July 29, 1958 2,951,022 Hartzband et al. Aug. 30, 1960 FOREIGN PATENTS 309,002 Great Britain Apr. 2, 1929 OTHER REFERENCES Mincher Knolls Atomic Power Laboratory Report 731, pp. 1-8, April 2, 1952. 

1. A PROCESS WHICH COMPRISES EXPOSING A HYDROCARBON MIXTURE BOILING IN THE RANGE OF 300 TO 700*F. AND CONSISTING ESSENTIALLY OF 60 TO 95 WEIGHT PERCENT OF SATURATED HYDROCARBONS, 5 TO 40 WEIGHT PERCENT OF UNSATURATED HYDROCARBONS, LESS THAN 2 WEIGHT PERCENT OF AROMATICS, AND LESS THAN 25 WEIGHT PERCENT OF NAPHTHENES, TO RADIATION COMPRISING NEUTRONS AND GAMMA RAYS HAVING AN ENERGY ABOVE 1 MEV. OBTAINED FROM A NUCLEAR REACTOR, AT A TEMPERATURE IN THE RANGE OF 100* TO 600*F., A DOSE RATE ABOVE 1 EQUIVALENT MEGAROENTGENS PER HOUR, UNTIL 100 TO 1400 EQUIVALENT MEGAROENTGENS HAVE BEEN ABSORBED, AND RECOVERING FROM THE IRRADIATED MIXTURE A HIGH QUALITY LUBRICATING FRACTION BOILING ABOVE 700*F., HAVING A VISCOSITY ABOVE 35 SSU AT 210*F. AND A VISCOSITY INDEX ABOVE 125 AND AMOUNTING TO AT LEAST 50 WEIGHT PERCENT OF SAID HYDROCARBON MIXTURE. 